This invention relates to a one-way clutch using rollers as engaging elements.
One-way clutches in which rollers are engaging elements, such as that disclosed in Japanese patent publication 47-43645, are known. With these one-way clutches, as shown in FIGS. 16 and 17, between the inner peripheral surface of an outer hollow member (outer member) 61 and the outer peripheral surface of an inner shaft member (inner member) 62, rollers 63 are housed in a so-called full-type state so as to surround the inner shaft member 62 while abutting each other. Each roller 63 is adapted to engage one of a plurality of inclined cam surfaces 64 formed on the inner peripheral surface of the outer hollow member 61 in one direction due to the wedge effect. When the outer hollow member 61 rotates clockwise or the inner shaft member 62 rotates counterclockwise, each roller 63 engages its respective cam surface 64, so that torque is transmitted.
With the one-way clutch shown in FIG. 16, the rollers 63 are housed so as to surround the entire circumference of the inner shaft member 62. When the outer hollow member 61 or the inner shaft member 62 rotates in the above-said rotational direction, due to the frictional force between the rotary members and the rollers 63, the rollers are adapted to engage the cam surfaces 64. In this embodiment, when frictional force acts on one of the rollers 63, since the rollers engage with one another, all the rollers engage the cam surfaces 64.
With the one-way clutch shown in FIG. 17, one of the rollers 63 housed in a full-type state is replaced with a spring roller 65. Due to the resilience accompanying its resilient deformation, the spring roller 65 urges the adjacent roller 63, so that all the rollers abutting one another engage the cam surfaces 64. Instead of the spring roller 65, a resilient roller such as a rubber roller or a resilient member such as a leaf spring may also be used.
Such full type one-way clutches aim to increase the torque-transmitting capability by increasing the number of rollers arranged and to make a compact design possible by eliminating a cage for rollers.
These conventional full type one-way clutches have the following problems. With the one-way clutch shown in FIG. 16, because the production of frictional force is unstable, it is impossible to reliably bring the rollers into engagement with the cam surfaces, so that the clutch sometimes does not operate.
On the other hand, with a one-way clutch of the type shown in FIG. 17, since the resilient member disposed between the rollers housed in a full-type state such as a spring roller sometimes shrinks excessively due to resilient deformation, a space may be formed between any adjacent rollers or between the resilient member and the adjacent roller, thus making it impossible to instantly and reliably transmit the biasing force of the resilient member to all the rollers. This may cause a lowering of the torque-transmitting capability or a delay in turning on and off the clutch.
An object of this invention is to provide a full type one-way clutch that is superior in responsiveness without lowering the torque-transmitting capability.
According to this invention, there is provided a one-way clutch comprising an outer member having an inner peripheral surface, and an inner member having an outer peripheral surface. One of the inner and outer peripheral surfaces is formed with a plurality of inclined cam surfaces, and the other is formed into a cylindrical surface. Rollers used as engaging members are arranged between the outer member and the inner member at positions so as to oppose the cam surfaces, and a resilient member is provided for biasing the rollers in such a direction as to engage the cam surfaces. The rollers are brought into abutment with one another directly or through auxiliary rollers having a smaller diameter than the rollers. The resilient member is brought into engagement with the inner peripheral surface of the outer member or the outer peripheral surface of the inner member to transmit the biasing force of the resilient member to all of the rollers through the rollers abutting one another.
By engaging the roller-biasing resilient member on the inner peripheral surface of the outer member or the outer peripheral surface of the inner member, all the rollers can always maintain a mutually abutting state directly or through the auxiliary rollers without any resilient members disposed between the rollers. Therefore, it is possible to reliably and instantly transmit the biasing force of the resilient members to all the rollers.
By making at least one of the inner member and outer member of a sintered metal or by blanking a steel plate, it is possible to manufacture the outer member and inner member at a low cost.
If the blanking is fine-blanking to the finished dimension of the outer member or inner member, it is possible to eliminate finish working such as shaving and reduce the occurrence of thermal strain during heat treatment.
By disposing the auxiliary rollers at positions where the resilient members are provided, it is possible to increase the space for receiving the resilient members, and to increase the biasing force to the rollers by use of a larger resilient member.
As the resilient members, steel springs having a tongue for biasing the rollers may be used.
By integrally forming a torque-transmitting means on the outer periphery of the outer member, it is possible to reduce the number of parts and simplify the mounting work of the clutch.
The torque-transmitting means may be ribs formed on the outer periphery of the outer member.
By replacing at least one of the rollers with an engaging element having the same outer diameter as the rollers but having a different shape therefrom, it is possible to improve the retaining ability of grease and oil on the cam surfaces and the cylindrical surface, and thus to reduce the idling torque of the one-way clutch.
As the engaging element having a different shape, a grooved roller formed with at least one annular groove on the cylindrical surface of the roller, or a short roller shorter in length than the other rollers may be used.
By forming independent, minute recesses in the surface of the rollers in a random manner, it is possible to form a sufficient oil film on the surfaces of the rollers, to reduce the idling torque, and to suppress wear due to sliding during idling.
If the surface of the rollers formed with the recesses has an average surface roughness that, when indicated in terms of minimum root mean square RMS, the ratio RMS (L)/RMS (C) of the axial average surface roughness RMS (L) of the rollers to the circumferential average surface roughness RMS (C) is not more than 1.0, and the SK value, which is a parameter of surface roughness, is not more than xe2x88x921.6 both in the axial and circumferential directions of the rollers, an oil film can be more easily formed for circumferential sliding of the rollers. Therefore, it is possible to improve the suppressing effect of wear due to sliding during idling.
Such surfaces of the rollers can be formed by special barrel polishing. The SK value represents the degree of balance of the distribution of protrusions and recesses with reference to the reference surface. If they are distributed symmetrically with respect to the reference surface, the SK value will be zero. The greater the rate of recesses to protrusions, the greater the negative value. Thus, by setting the SK value at xe2x88x921.6 or lower, it is possible to provide sufficient oil-retaining recesses.
By forming, in the inner peripheral surface of the outer member or the outer peripheral surface of the inner member formed with the cam surfaces, at least one groove extending in the axial direction, and by engaging the resilient member in the groove, it is possible to facilitate the mounting of the resilient members.
By having one end of the resilient member tapered, it is possible to insert the resilient member from the tapered end and smoothly mount it without forcibly deflecting it.
By providing side plates for guiding both end faces of the rollers, and by providing a means for engaging the side plate to the end face of the outer member or inner member, it is possible to prevent the rollers from coming out and to simplify the assembling of the one-way clutch.
The means for engaging the side plate may be protrusions formed on the side plate at a plurality of points so as to engage recesses formed in the end face of the outer member or inner member.
By forming the cam surfaces on the outer periphery of the inner member, bringing the resilient member into engagement with the outer periphery of the inner member, and forming a torque-transmitting means on the inner periphery of the inner member, it is possible to minimize the influence of centrifugal force by making the rollers stationary during idling if the outer member is a rotation-transmitting side. For example, the outer member can be a clutch for a stator in a torque converter so as to stabilize the idling properties.
The torque-transmitting means formed on the inner periphery of the inner member may be a serration.
With the one-way clutch in which the cam surfaces are formed on the outer periphery of the inner member, by forming an annular groove in an inner cylindrical surface of the outer member, it is possible to increase the ability to retain grease on the cylindrical surface and thus to reduce the idling torque.
With the one-way clutch in which the cam surfaces are formed on the outer periphery of the inner member, by mounting it in a stator of a torque converter, it is possible to assure excellent clutch properties and reduce the cost.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: